Ultra-high flux loose nanofiltration membrane based on metal organic framework (CAU-10-H)/P84 co-polyimide for dye/salt fractionation from industrial waste water

In recent times, loose nanofiltration (NF) membranes have gained popularity for the treatment of dye/salt industrial wastewater, primarily owing to their exceptional separation capabilities and economic advantages. However, achieving nanocomposite mixed matrix membranes with ultrahigh water permeance and specific pore and surface characteristics for effective dye and inorganic salt fractionation presents a significant challenge. This study focuses on the development of high-efficiency loose nanofiltration mixed matrix membranes (MMMs) achieved by combining polymers and porous nanoparticles. Metal-organic frameworks (MOFs) hold substantial promise as porous additives in MMMs. However, high-quality MOF-based MMMs for treating dye/salt aqueous solutions are still scarce. In this work, we synthesized an aluminum-based metal-organic framework (CAU-10-H) and utilized it in the fabrication of composite MMMs by blending it with co-polyimide (P84). We successfully created a thin and porous CAU-10-H/P84 layer with a significantly low MOF content (1.5 %) on a nylon support. Our research findings revealed that the optimized membrane exhibited desirable permeance (260.4 LMH/bar) for dye/salt solutions and a pure water permeance of 386.4 LMH/bar. Furthermore, the membrane demonstrated high dye rejection (99.2 % for methyl blue and 99.1 % for Congo red) while maintaining low salt rejection (4.8 % for NaCl and 16.3 % for Na₂SO₄). Additionally, the composite MMMs exhibited excellent stability throughout a 24-h filtration process. The CAU-10-H/P84 composite MMMs exhibit significant potential for applications in dye/salt fractionation.